A method of reducing propagation of threading dislocations into active areas of an optoelectronic device having a III–V material system includes growing a metamorphic buffer region in the presence of an isoelectronic surfactant. A first buffer layer may be lattice matched to an adjacent substrate and a second buffer layer may be lattice matched to device layers disposed upon the second buffer layer. Moreover, multiple metamorphic buffer layers fabricated in this manner may be used in a single given device allowing multiple layers to have their band gaps and lattice constants independently selected from those of the rest of the device.
Legal claims defining the scope of protection, as filed with the USPTO.
1. A method of reducing threading dislocations in active areas of an optoelectronic device, comprising the steps of: growing a plurality of epitaxial buffer layers forming a metamorphic buffer region with a graded lattice constant; relaxing said buffer layers through a dislocation glide mechanism during epitaxial growth of said buffer layers; forming dislocation loops made up of threading dislocations during relaxation of said buffer layers; introducing an isoelectronic surfactant during said epitaxial growth of at least one of said buffer layers without changing the charge-carrier concentration of said at least one of said buffer layers; slowing down the formation rate of said dislocation loops in the presence of said isoelectronic surfactant; and reducing the propagation of said threading dislocations into active areas of said optoelectronic device in the presence of said isoelectronic surfactant.
2. The method of claim 1 , further comprising the step of: providing said isoelectronic surfactant in form of at least one precursor.
3. The method of claim 1 , further comprising the step of providing said isoelectronic surfactant as a low vapor pressure element that does not readily incorporate into said epitaxial buffer layers.
4. The method of claim 1 , further comprising the step of additionally relaxing said buffer region in the presence of said isoelectronic surfactant.
5. The method of claim 1 , further comprising the step of introducing said isoelectronic surfactant during a pause in said epitaxial growth of a single buffer layer.
6. The method of claim 1 , further comprising the step of introducing said isoelectronic surfactant at the start of said epitaxial growth of a single buffer layer.
7. The method of claim 1 , further comprising the step of obtaining said graded lattice constant of said metamorphic buffer region by increasing weight percentages of at least one element in the composition of said buffer from a lowermost portion to an uppermost portion, wherein said at least one element is different from said isoelectronic surfactant.
8. The method of claim 1 , further comprising the step of obtaining said graded lattice constant of said metamorphic buffer region by decreasing weight percentages of at least one element in the composition of said buffer layers from a lowermost portion to an uppermost portion, wherein said at least one element is different from said isoelectronic surfactant.
9. The method of claim 1 , wherein said device includes one of tensile strained epitaxial layers and compressively strained epitaxial layers.
10. A method of growing an optoelectronic device having a III–V material system, comprising: epitaxially growing a lowermost buffer layer immediately adjacent and lattice-matched to a substrate having a first lattice constant; epitaxially growing at least one intermediate buffer layer above said lowermost buffer layer, wherein said intermediate buffer layer has a second lattice constant that is different from said first lattice constant; epitaxially growing an uppermost buffer layer above said intermediate buffer layer and immediately adjacent and lattice-matched to a device layer having a third lattice constant that is different from said first and said second lattice constant such that said first, said second, and said third lattice constant are graded; altering a material composition of said III–V material system to create a metamorphic buffer region with a graded lattice constant confined by said lowermost buffer layer and said uppermost buffer layer; introducing a first isoelectronic surfactant during the epitaxial growth of at least one buffer layer of said buffer region without changing the charge-carrier concentration of said at least one buffer layer; controlling the rate of nucleation of threading dislocations in the presence of said first isoelectronic surfactant by slowing down the formation rate of dislocation loops; reducing the propagation of said threading dislocations into active areas of said optoelectronic device in the presence of said first isoelectronic surfactant; allowing at least one of said buffer layers to relax in the presence of said first surfactant; and allowing said first isoelectronic surfactant to desorb prior to said epitaxially growth of an adjacent buffer layer.
11. The method of claim 10 , further comprises the step of introducing said first isoelectronic surfactant in the form of a precursor where the amount of said isoelectronic surfactant to group-III element is in the range from about 0.001 to about 1.0 in the vapor phase.
12. The method of claim 10 , further comprising increasing a concentration of an element in said material composition from said lowermost buffer layer to said uppermost buffer layer.
13. The method of claim 10 , further comprising decreasing a concentration of an element in said material composition from said lowermost buffer layer to said uppermost buffer layer.
14. The method of claim 10 , wherein altering said material composition includes changing said material composition in a stepped fashion.
15. The method of claim 10 , wherein altering said material composition includes changing said material composition in a smooth fashion.
16. The method of claim 10 , further comprising introducing a second isoelectronic surfactant into at least another of said buffer layers.
17. The method of claim 10 , wherein introducing said first surfactant includes adding said first surfactant at a start of said growth of said at least one buffer layer.
18. The method of claim 10 , wherein introducing said first surfactant includes adding said first surfactant during a pause of said growth of said at least one buffer layer.
19. The method of claim 18 , further comprising pausing said growth for about 0.01 to about 5 minutes.
20. The method of claim 10 , wherein said material system comprises GaInP.
21. The method of claim 20 , wherein said first surfactant comprises Sb and said first surfactant is introduced according to a molar ratio of TESb/(TMGa+TMIn) wherein TESb is triethylantimony, TMGa is trimethylgallium, and TMIn is trimethyindium.
22. The method of claim 21 , wherein said ratio is between about 1×10 −5 to 1×10 5 .
23. The method of claim 10 , wherein said device comprises a solar cell.
24. A method of growing an optoelectronic device having a III–V material system, comprising: growing a first layer on top of a substrate; wherein said first layer is lattice matched to said substrate; introducing a first isoelectronic surfactant into said lattice matched first layer without changing the charge-carrier concentration of said first layer; growing a second layer on top of said first layer; wherein said second layer is lattice mismatched to said substrate; and allowing said lattice mismatched second layer to relax in the presence of said first surfactant the grown device being optoelectronic having a III–V material system.
25. The method of claim 24 , wherein introducing said first surfactant comprises introducing a low vapor pressure group III or group V element.
26. The method of claim 24 , wherein said lattice matched first layer includes a metamorphic buffer region.
27. The method of claim 26 , further comprising altering a concentration of an element in a material composition of said buffer region from a lowermost portion of said buffer region to an uppermost portion of said buffer region to achieve a graded lattice constant within said buffer region.
28. The method of claim 27 , wherein altering said material composition includes changing said material composition in a stepped fashion.
29. The method of claim 27 , wherein altering said material composition includes changing said material composition in a smooth fashion.
30. The method of claim 24 , wherein introducing said first surfactant includes adding said first surfactant at a start of said growth of said lattice matched first layer.
31. The method of claim 24 , wherein introducing said first surfactant includes adding said first surfactant during a pause of said growth of said lattice matched first layer.
32. The method of claim 24 , wherein said material system comprises GaInP.
33. The method of claim 24 , wherein said first surfactant comprises Sb and said first surfactant is introduced according to a molar ratio of TESb/(TMGa+TMIn) wherein TESb is triethylantimony, TMGa is trimethylgallium, and TMIn is trimethyindium.
34. The method of claim 33 , wherein said ratio is between about 0.001 to 1.0.
35. The method of claim 24 , wherein said device comprises a solar cell.
Cooperative Patent Classification codes for this invention. Click any code to explore related patents in that topic.
October 23, 2002
October 17, 2006
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